Comparisons of the acoustic radiation force of ultrasonic standing waves in half-wavelength and quarter-wavelength micro-resonators of cylindrical geometry.

Ultrasonic standing waves with specific wavelengths generated in the multi-layered micro-resonators were numerically and experimentally analyzed. Using a three-dimensional scanning fluorescence microscope, the acoustophoretic motion of fluorescent microparticles within the micro-resonators was carefully and accurately measured. The manufactured micro-resonators were validated by comparing the location of the acoustic pressure nodal plane and the average energy density curves derived from numerical and experimental results. Results confirmed that the acoustic radiation force of the induced ultrasonic standing waves drives the microparticles vertically within the micro-resonators and their average energy density increases as the sinusoidal voltage applied to the piezoelectric transducer increases. Semi-empirical correlations were developed for the average energy density, based on experimental results for a wide range of the applied voltage amplitudes. The correlations were in good agreement, within less than 20 % of the experimental values measured for both the half-wavelength and quarter-wavelength micro-resonators.

Strength and Permeability Properties of Pervious Concrete Containing Coal Bottom Ash Aggregates.

This study investigates the strength and permeability properties of pervious concrete-containing coal bottom ash (CBA) aggregates. Two pervious concrete mixtures were fabricated with different aggregate size distributions. One mixture contained CBA aggregates with a single-type distribution and the other mixture contained CBA aggregates with a hybrid-type distribution. The test parameters of the CBA pervious concrete included the water/cement (W/C) ratio and compaction level to investigate their effects on the properties. W/C ratios of 0.25, 0.30, and 0.35 were considered for the mixture, and compaction levels of 0.5, 1.5, and 3.0 MPa were applied to fabricate the pervious specimen. The increase in the W/C ratio reduced the strength by approximately 20% to 30% of the CBA pervious concrete. The increase in the compaction level reduced the permeability by approximately four to five times but significantly increased the strength of the CBA pervious concrete. The test results indicate that the use of single-type CBA or hybrid CBA aggregates with different size distributions affected the properties of the pervious concrete. The strength of specimens, including hybrid CBA aggregates, was 30% to 45% greater than that of the specimens containing single-type CBA aggregates. Meanwhile, the use of hybrid CBA aggregates reduced the permeability of the CBA pervious concrete by approximately 20% to 35%. Finally, relationships between the strength properties, permeability characteristics and total void ratios of the CBA pervious concrete specimens are suggested based on the test results.

A Comparative Study of the Thermal Conductivities of CBA Porous Concretes.

Porous concrete has recently gained increasing attention in the construction industry. To improve the properties of porous concrete, coal bottom ash (CBA) was used as the aggregate in the concrete mixtures studied herein. Hybrid CBA aggregates, including a 20% proportion of particles with sizes of 1.2~2.5 mm and an 80% proportion of particles with sizes of 2.5~5.0 mm, were used in the mixtures. Various water/cement ratios ranging from 0.25 to 0.35 were used in the mixtures. The effects of compaction at 0.5, 1.5, and 3.0 MPa on the properties of the porous concrete were also examined. The increase in the water/cement ratio reduced the unit weight and thermal conductivity while increasing the porosity of the porous concrete. Although the compaction had a significant impact on the other properties of the porous concrete, the thermal property was not significantly influenced. By using CBA in porous concrete, the mechanical and thermal properties of the concrete were significantly improved. Finally, the relationships between the thermal conductivity and other properties of the porous concrete were investigated.

Interlayer Strength of 3D-Printed Mortar Reinforced by Postinstalled Reinforcement.

This work was designed to evaluate the interlayer strength of 3D-printed mortar with postinstalled interlayer reinforcement. Two methods of postinstalled interlayer reinforcement were considered according to the amount of overlapping. The first method did not include overlapping of the interlayer reinforcement, while the second method included overlap lengths of 20 and 40 mm. Additionally, two different curing conditions were considered: air-curing conditions and water-curing conditions. The compressive, splitting tensile, and flexural tensile strengths of 3D-printed mortar specimens with different reinforcement methods and curing conditions were investigated under three loading directions. The three loading directions were defined based on the three planes of the printed specimens. The compressive, splitting tensile, and flexural tensile strengths were dependent on the loading directions. In particular, the splitting and flexural tensile strengths decreased considerably when tensile stresses acted on the interlayers of the 3D-printed mortar specimens. However, when longitudinal interlayer reinforcement penetrated the printed layers, the flexural tensile strength or interlayer bonding strength of the printed specimens increased significantly at the interlayers. In addition, mortar specimens reinforced with overlap lengths of 20 and 40 mm were investigated in this study. The flexural tensile strength or interlayer bonding strength of 3D-printed mortar decreased after treatment under air-curing conditions because the interlayers of the printed mortar formed more pores under these conditions and were more vulnerable under loading. Finally, the findings of this study suggested that interlayer reinforcement is a potential method for improving the interlayer bonding strength of 3D-printed mortar.

Selected Strength Properties of Coal Bottom Ash (CBA) Concrete Containing Fly Ash under Different Curing and Drying Conditions.

This study aims to evaluate the effect of curing and drying conditions on the strength properties of concrete containing coal bottom ash (CBA) and fly ash as substitutes for fine aggregates and cement, respectively. The strength properties of the concrete including CBA and fly ash were evaluated under two different curing and drying conditions: saturated surface-dry (SSD) conditions and oven-dried conditions at curing ages of 28 and 91 days. The natural fine aggregates of the mixtures were replaced by CBA fine aggregates at 25%, 50%, 75%, and 100% by volume. In addition, the cement in the mixtures was partly replaced with fly ash at 20% and 40%. The experimental program included the measurement of the unit weight, compressive strength, splitting tensile strength, flexural strength, and ultrasonic pulse velocity of the concrete. The test results showed that the compressive strength, splitting tensile strength, and flexural strength decreased as the CBA content increased under both SSD and oven-dried conditions. The curing and drying conditions of the concrete with CBA and fly ash considerably influenced the reduction in the compressive, splitting, and flexural tensile strengths of the concrete. Additionally, the experimental results showed that fly ash insignificantly contributed to the reduction in the strength properties under both SSD and oven-dried conditions. Finally, the relationships between ultrasonic pulse velocity and the splitting tensile strength, flexural tensile strength, and compressive strength were investigated.

Buildability and Mechanical Properties of 3D Printed Concrete.

Recently, 3D concrete printing has progressed rapidly in the construction industry. However, this technique still contains several factors that influence the buildability and mechanical properties of the printed concrete. Therefore, this study investigated the effects of the nozzle speed, the interlayer interval time, the rotations per minute (RPMs) of the screw in the 3D printing device, and the presence of lateral supports on the buildability of 3D concrete printing. In addition, this paper presents the results of the mechanical properties, including the compressive, splitting tensile, and flexural tensile strengths of 3D printed concrete. The buildability of 3D printed structures was improved with an extended interlayer interval time of up to 300 s. The printing processes were interrupted because of tearing of concrete filaments, which was related to excessive RPMs of the mixing screw. The test results also showed that a lateral support with a wide contact surface could improve the resistance to buckling failure for 3D printed structures. The test results of the mechanical properties of the 3D printed concrete specimens indicated that the compressive, splitting tensile, and flexural tensile strengths significantly depended on the bonding behavior at the interlayers of the printed specimens. In addition, although metal laths were expected to improve the tensile strength of the printed specimens, they adversely affected the tensile performance due to weak bonding between the reinforcements and concrete filaments.

Fully-automatic deep learning-based analysis for determination of the invasiveness of breast cancer cells in an acoustic trap.

A single-beam acoustic trapping technique has been shown to be very useful for determining the invasiveness of suspended breast cancer cells in an acoustic trap with a manual calcium analysis method. However, for the rapid translation of the technology into the clinic, the development of an efficient/accurate analytical method is needed. We, therefore, develop a fully-automatic deep learning-based calcium image analysis algorithm for determining the invasiveness of suspended breast cancer cells using a single-beam acoustic trapping system. The algorithm allows to segment cells, find trapped cells, and quantify their calcium changes over time. For better segmentation of calcium fluorescent cells even with vague boundaries, a novel deep learning architecture with multi-scale/multi-channel convolution operations (MM-Net) is devised and constructed by a target inversion training method. The MM-Net outperforms other deep learning models in the cell segmentation. Also, a detection/quantification algorithm is developed and implemented to automatically determine the invasiveness of a trapped cell. For the evaluation of the algorithm, it is applied to quantify the invasiveness of breast cancer cells. The results show that the algorithm offers similar performance to the manual calcium analysis method for determining the invasiveness of cancer cells, suggesting that it may serve as a novel tool to automatically determine the invasiveness of cancer cells with high-efficiency.

An Experimental Study on the Ductility and Flexural Toughness of Ultrahigh-Performance Concrete Beams Subjected to Bending.

Ultrahigh-performance concrete (UHPC) and high-strength concrete (HSC) are currently widely used because of their distinct superior properties. Thus, a comprehensive comparison of the flexural behavior of UHPC and HSC beams is presented in this study. Nine UHPC beams and three HSC beams were subjected to pure bending tests to investigate the effect of various reinforcement ratios and steel fiber volume contents on the cracking and failure patterns, load-deflection behavior, ductility, and flexural toughness of these beams. The addition of steel fibers in the UHPC improved the energy absorption capacity of the beams, causing the UHPC beams to fail via rebar fracture. The deflection and curvature ductility indices were determined and compared in this study. The ductility indices of the HSC beam tended to decrease sharply as the rebar ratio increased, whereas those of the UHPC beam did not show a clear trend with respect to the rebar ratio. In addition, a comparison between the results in this study and the results from previous studies was performed. In this study, the addition of steel fiber contents up to 1.5% in UHPC increased the load capacity, ductility, and flexural toughness of the UHPC beams, whereas the addition of a steel fiber content of 2.0% did not significantly increase the ductility or flexural toughness of the UHPC beams.

A Study on the Thermal Properties of High-Strength Concrete Containing CBA Fine Aggregates.

The thermal conductivity of concrete is a key factor for efficient energy consumption in concrete buildings because thermal conductivity plays a significant role in heat transfer through concrete walls. This study investigated the effects of replacing fine aggregates with coal bottom ash (CBA) and the influence of curing age on the thermal properties of high-strength concrete with a compressive strength exceeding 60 MPa. The different CBA aggregate contents included 25%, 50%, 75%, and 100%, and different curing ages included 28 and 56 days. For concrete containing CBA fine aggregate, the thermal and mechanical properties, including the unit weight, thermal conductivity, compressive strength, and ultrasonic velocity, were measured. The experimental results reveal that the unit weight and thermal conductivity of the CBA concrete were highly dependent on the CBA content. The unit weight, thermal conductivity, and compressive strength of the concrete decreased as the CBA content increased. Relationships between the thermal conductivity and the unit weight, thermal conductivity and compressive strength of the CBA concrete were proposed in the form of exponential functions. The equations proposed in this study provided predictions that were in good agreement with the test results. In addition, the test results show that there was an approximately linear relationship between the thermal conductivity and ultrasonic velocity of the CBA concrete.

A Micromachined Metal Oxide Composite Dual Gas Sensor System for Principal Component Analysis-Based Multi-Monitoring of Noxious Gas Mixtures.

Microelectronic gas-sensor devices were developed for the detection of carbon monoxide (CO), nitrogen dioxides (NO2), ammonia (NH3) and formaldehyde (HCHO), and their gas-sensing characteristics in six different binary gas systems were examined using pattern-recognition methods. Four nanosized gas-sensing materials for these target gases, i.e., Pd-SnO2 for CO, In2O3 for NOX, Ru-WO3 for NH3, and SnO2-ZnO for HCHO, were synthesized using a sol-gel method, and sensor devices were fabricated using a microsensor platform. Principal component analysis of the experimental data from the microelectromechanical systems gas-sensor arrays under exposure to single gases and their mixtures indicated that identification of each individual gas in the mixture was successful. Additionally, the gas-sensing behavior toward the mixed gas indicated that the traditional adsorption and desorption mechanism of the n-type metal oxide semiconductor (MOS) governs the sensing mechanism of the mixed gas systems.

Acoustic Trapping Technique for Studying Calcium Response of a Suspended Breast Cancer Cell: Determination of Its Invasion Potentials.

A noncontact single-beam acoustic trapping technique has proven to be a promising tool for cell manipulation and characterization that provide essential knowledge for a variety of biomedical applications. Here, we investigated cell characteristics as to whether the calcium responses of suspended breast cancer cells to different acoustic trapping forces are related to their invasiveness. For this, we combined a single-beam acoustic trapping system with a 30-MHz press-focused lithium niobate ultrasound transducer and an epifluorescence microscope. Using the system, intracellular calcium changes of suspended MDA-MB-231 (highly invasive) and MCF-7 (weakly invasive) cells were monitored while trapping the cells at different acoustic pressures. The results showed that a single suspended breast cancer cell isolated by the acoustic microbeam behaved differently on the calcium elevation in response to changes in acoustic trapping force, depending on its invasiveness. In particular, the MDA-MB-231 cells exhibited higher calcium elevation than MCF-7 cells when each cell was trapped at low acoustic pressure. Based on these results, we believe that the single-beam acoustic trapping technique has high potential as an alternative tool for determining the degree of invasiveness of suspended breast cancer cells.

Gravitational field flow fractionation: Enhancing the resolution power by using an acoustic force field.

An acoustic field flow fractionation (FFF) device was developed to fractionate a micro-particle mixture on the basis of the particle diameter using an acoustic force field in a carrier liquid flow. In the acoustic FFF channel used in the device, ultrasound waves generated from piezoelectric transducers driven by a sinusoidal signal of 2.02 Mhz propagated into the carrier liquid flow and built up a quarter-wavelength ultrasound standing wave field across the channel height. It was experimentally demonstrated that the acoustic field with a pressure node plane at the bottom surface of the channel reduced the thickness of the particle diffusion layer in a stagnant liquid proportional to the applied voltage driving the piezoelectric transducer. In the size-dependent particle separation, the particle mixture flowing through the acoustic FFF channel experienced an acoustic radiation force in the gravitational direction. As a result, suppressing the diffusion of small particles, particles were transported along the bottom surface of the channel with the local velocity of the carrier liquid at the particle center. The developed acoustic FFF device successfully fractionated a fluorescent micro-particle mixture (1, 3, 5, and 10 µm diameter), whereas the 3 and 5 µm particles were not fractionated in the FFF device using only the gravitational force field due to the diffusion of 3 µm particles.